Real basic stuf starting out home assistant

Hi everyone,
I’m just starting out using home assistant.
I’m struggling understanding how it works by a developer’s point of view, and I would like to know if there is an article or a video explaining the architecture of the software. It would make my life much easier understanding what I’m doing.
I have integrated google home following the guidelines on the home assistant web page but when I import the devices in the google home app they all appear as breaker, so, for example, I’m not able to change the volume on my tv but I’m just able to switch it on or turn it off, can you explain me why?